I have had 3 ct angiogram of chest within one year. should i be worried about the radiation?

Worrying would not do any good. The amount of radiations is not likely to affect your health. You can reduce your risk of cancer by adopting healthy habits: Eat a mostly vegetarian diet, avoid alcohol, tobacco and street drugs, avoid excessive exposure to sun, maintain healthy weight, get HPV vaccine, exercise 30 minutes each day, drink enough water so your urine is mostly colorless.